Error 500: Internal Server Error

URI
/utility/schedulemgt_list_user
Class
org.hibernate.ObjectNotFoundException
Message
No row with the given identifier exists: [com.TradeCourseExamRegistration#21]

Trace

    Line | Method
->> 2849 | valueOf               in java.lang.String
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
|    128 | debug                 in org.apache.commons.logging.impl.SLF4JLog
|    112 | createNode . . . . .  in de.andreasschmitt.export.builder.ExcelBuilder
|     45 | doCall                in de.andreasschmitt.export.exporter.DefaultExcelExporter$_exportData_closure1_closure2_closure3_closure6_closure7
|     43 | doCall . . . . . . .  in de.andreasschmitt.export.exporter.DefaultExcelExporter$_exportData_closure1_closure2_closure3_closure6
|     42 | doCall                in de.andreasschmitt.export.exporter.DefaultExcelExporter$_exportData_closure1_closure2_closure3
|     23 | doCall . . . . . . .  in de.andreasschmitt.export.exporter.DefaultExcelExporter$_exportData_closure1_closure2
|     22 | doCall                in de.andreasschmitt.export.exporter.DefaultExcelExporter$_exportData_closure1
|     21 | exportData . . . . .  in de.andreasschmitt.export.exporter.DefaultExcelExporter
|     19 | export                in de.andreasschmitt.export.exporter.AbstractExporter
|     20 | export . . . . . . .  in de.andreasschmitt.export.ExportService
|     15 | export                in     ''
|     99 | schedulemgt_list_user in com.UtilityController
|    195 | doFilter              in grails.plugin.cache.web.filter.PageFragmentCachingFilter
|     63 | doFilter . . . . . .  in grails.plugin.cache.web.filter.AbstractFilter
|   1145 | runWorker             in java.util.concurrent.ThreadPoolExecutor
|    615 | run . . . . . . . . . in java.util.concurrent.ThreadPoolExecutor$Worker
^    745 | run                   in java.lang.Thread